IDNTG - Mutations

Leveling Overview

Page Contents

Nuclear Throne follows a simple leveling system. Radiation that drops from enemies serves as experience points which will fill the rad meter. Once filled the character will level up, and upon exiting the current level they will be given a pool of skills to choose from that are known as mutations.

The player will always start at level 1 at the start of the run, and every consecutive level up will grant a mutation up to level 9. This means that a typical run will have 8 mutations, but a 9th can be gained through Crown of Destiny.

Reaching level 10 is referred to as 'ultra'. This gives character-specific mutation choices, which typically is an upgrade to that character's unique passive or active ability.

Any additional rads gained after reaching ultra will continue to fill the rad meter and is meant to be used as additional ammunition for ultra weapons. If the rad meter is fully filled out any additional rads gained will be wasted, similar to collecting pickups at full health/ammo.

The following table lists how many rads it takes to level up, as well as the total rads collected up to that point:

Level:	Lvl. 1	Lvl. 2	Lvl. 3	Lvl. 4	Lvl. 5	Lvl. 6	Lvl. 7	Lvl. 8	Lvl. 9	Ultra	Full Ultra
Rads needed:	0 Rads	61 Rads	120 Rads	180 Rads	240 Rads	300 Rads	360 Rads	420 Rads	480 Rads	540 Rads	600 Rads
Total Rads:	0 Rads	61 Rads	181 Rads	361 Rads	601 Rads	901 Rads	1,261 Rads	1,681 Rads	2,161 Rads	2,701 Rads	3,301 Rads

Leveling Mechanics

In a vanilla run, mutations can always be considered completely random. In reality there is a set mutation seed that dictates what mutations will be seen, which matters for replaying Weekly challenges or if Daily information is shared between players. There is a Daily Sheet to share information for both types of runs, however note that this includes many advanced mechanics.

This example image is from the daily sheet, and can be used to illustrate how basic leveling works in any run. The player starts from Set 1 and any time they level up, they advance to the next set. (Betas start from Set 0, which is relevant for daily/weeklies).

Only the four leftmost mutations are seen upon leveling up. The fifth mutation on the right is only seen with Horror's passive. If a mutation is taken from a set it gets removed from the mutation pool; for example if Sharp Teeth is taken in Set 1 then it will not reappear in Set 2, and Thronebutt will now appear in the normal set instead as the 4th slot.

If set logic seems confusing at all, weekly challenges can be played multiple times while taking different mutations each run to observe any differences in sets.

List of Mutations

There are 29 possible mutations to see when leveling up. 2 of which are 'rerolls' to see a new set and 1 is a secret mutation that only appears in a specific circumstance. Once a mutation is picked it is removed from the mutation pool.

Each character gets 2 unique ultra mutations, with Horror getting the choice of 3. This means there are 25 ultra mutations for normal characters, 6 for secret characters and 2 specifically for co-op.

Mutation descriptions will be listed as they are seen in-game with quotation marks. A detailed description of each mutation's mechanics will then be listed. Additional information for weapon-specific mutations can be found on the weapons page, while detailed information for character ultras and thronebutts can be found on individual character pages.

Normal Mutations
Back Muscle	"Higher Ammo Max" Increases max ammo capacity for shells, energy, bolts and explosives from 55 to 99. Increases max ammo capacity for bullets from 255 to 555. Pickups drop more when low on ammo (below 20% of max), while dropping less when high on ammo (above 60% of max), and as this is percentage based that means there is a higher threshold for increased drop rates while running Back Muscle. Full tech here.
Bloodlust	"Some Kills Regenerate HP" Any time an enemy is killed they have a 1 in 13 (7.69%) chance of healing the player 1 HP, applied automatically. Regardless of current HP this always has the same chance to heal, which differs from HP drops.
Boiling Veins	"No Damage From Explosions And Fire When Under 4 HP" (Poor flavor text, it's at or below 4 HP.) Any explosive or fire damage will not set the player below 4 HP, regardless of current max HP. It is impossible to die to these damage sources. Protection includes any explosive or fire damage from enemies, player weapons or props. It will not prevent self-damaging from blood weapons, or Shielders deflecting blood projectiles. Bug: Shielded projectiles that produce flames can still harm the player, but is fixed on the 2023 Beta/NTT v100. This includes flames produced from the Flare Gun and Flame Cannon, as well as any flame shell projectile. A hidden perk of Boiling Veins is that it will also force explosives to respect player iframes. Explosions typically do 5 damage twice for 10 HP, however only the first instance of damage will count. This also prevents multiple instances of explosions from damaging at once, which is mostly relevant to Crystal at higher HP values. (In simpler terms, all explosions only deal half damage. This is 5 damage for normal explosions, 8 damage for IDPD explosions and 12 damage for green explosions.)
Bolt Marrow	"Homing Bolts" Any weapon that uses bolts will now behave differently, seeking enemies along their path. Normal Bolts: May slightly adjust its location to make contact/pierce an enemy that it would have missed. Heavy Bolts: Similar to normal bolts, but with a much weaker effect. Splinters: May adjust to nearby enemies to hit them instead, without piercing. Seekers: Increased homing radius to lock on targets much sooner and will take much shaper turns. Discs: May adjust to hit nearby enemies and will decrease its speed while passing through, being more likely to damage a target multiple times.
Eagle Eyes	"Better Accuracy" The closer to 0 a players accuracy is, the lower a weapons spread will be. Eagle Eyes multiplies the current value by 0.3. Normal characters have a default accuracy of 1, bringing it to 0.3. Steroids has a default accuracy of 1.8, bringing it to 0.54. Skeleton has a default accuracy of 1.5, bringing it to 0.45.
Euphoria	"Slower Enemy Bullets" Any projectiles shot by enemies now go 20% slower. Does not effect enemy speed in any way. Shields deflecting projectiles are not slowed, neither are some non-projectile attacks such as lasers.
Extra Feet	"More Speed, Walk Normal On All Terrain" Different floors will no longer effect the player, being sticky cobwebs and slippery ice. Adds 0.5 to the total speed. Mutants default speed is 4, bringing it to 4.5. Plant's speed is 4.5, bringing it to 5. Skeleton's speed is 3, bringing it to 3.5. Big Dog's speed is 2, bringing it to 2.5. (Technical note; these values are based on the games code before friction is applied.)
Gamma Guts	"Enemies Touching You Take Damage" Any enemies that come in contact with the player now take contact damage, at 6 damage a tick. Standing still does 1 tick of damage at a time, while moving does 2 ticks of damage at a time, meaning that moving around causes it to deal 12 damage. Enemies still deal contact damage, but if they are at 12 HP or below while the player is moving they will die before damaging the player. When an enemy dies to Gamma Guts it will cause a small shock that does 8 damage to any enemies directly around it. Props and Vans are unaffected by Gamma Guts.
Hammerhead	"Push Through A Limited Number Of Walls" The player can break up to 20 wall tiles in any level by directly walking into them. A special audio cue will play once all 20 tiles are used up to signify that no more walls can be broken that level.
Impact Wrists	"Corpses Fly & Hit Harder" Enemy corpses will fly a lot further and deal additional damage. Corpses travel long enough that they can deal damage to enemies multiple times, but will respect enemy iframes. Non-Beta/2021 Beta: Bugged. This only doubles corpse damage from 1 to 2 per hit. NTT v100/2023 Beta: Fixed. Corpses now deal damage based on velocity, doing 5 damage per hit at max speed while decreasing in damage as it slows down.
Laser Brain	"Energy Weapons Deal More Damage" Any weapon that uses energy ammo will deal additional damage. Each weapon laser type differs from each other, so 'additional damage' is rarely a flat percentage increase but rather higher damage potential. (Full damage values on weapons page.) Laser Weapons: Has the beam last longer allowing for further damage and piercing. Laser Cannon: Adds two additional laser beams on top of the increased laser damage, nearly doubling its damage. Lightning Weapons: Makes rails last longer to hit any individual enemy a 3rd time, allowing for up to 21 damage instead of 14. Lightning Cannon: Main ball's damage increased from 40 to 50, and lightning from it can hit any enemy a 3rd time as well. Plasma Weapons: All plasma balls last longer allowing for further damage and piercing. Plasma Explosions: Does not deal any extra damage. In Devastator's case, the invisible projectile moves slower to damage more enemies and spawn more plasma explosions. Energy Melee: Lasts long enough to hit enemies a second time, doubling their damage.
Long Arms	"More Melee Range" Any melee weapon gains more range, including melee that uses ammo.
Lucky Shot	"Some Kills Regenerate Ammo" Any time an enemy is killed they have a 2 in 17 (11.67%) chance of giving the player 1 drops worth of ammo applied automatically. The ammo given can be any one of the 5 ammo types, regardless of weapons are currently held or ammo levels.
Open Mind	"Extra Chest Spawn" Every level will include an additional chest spawn. This is randomly chosen between a weapon chest, ammo chest and rad canister and any of their special variations. Open Mind can spawn two of most chest variations such as two IDPD chests, two overflowing rad cans, two cursed chests. It cannot spawn two health chests or two big weapon chests at the same time. (However, two cursed big weapon chests still can.) Skipping 2 rad cans in the same level will cause Hostile Horror to spawn in the next. Only one overflowing rad can will convert into a Hostile Horror, however.
Plutonium Hunger	"Attract Drops And Rads From Further" Substantially increases the pickup range for drops. Ammo & HP drops can be reached from much further away, as just walking near a pickup will attract it. Rads pickup range will be increased to cover the majority of the screen, meaning just walking in the general direction of rads is enough to collect them.
Rabbit Paw	"More HP And Ammo Drops" All enemies gain a flat +40% drop rate for ammo. As HP drops are converted from ammo, this in turn gives HP more chances to appear as well.
Recycle Gland	"Most Hit Bullets Become Ammo" Most weapons that use bullet ammo will have a 60% chance of returning that ammo to the player automatically. Normal bullets hit have a chance to return 1 ammo, while heavy bullets have a chance to return 2 ammo. Weapons that use shell projectiles are not effected even if they use bullet ammo - these include Pop Gun, Pop Rifle & Incinerator. Shotgun Shoulders works on these weapons instead.
Rhino Skin	"+4 Max HP" Increases the player's maximum HP by 4. This automatically heals for the 4 new HP as well upon entering the next level.
Scarier Face	"Less Enemy HP" Every enemy will have 20% of their max HP removed permanently, rounded to the nearest whole number. This includes any enemies spawned midway into the level, bosses and Vans. Props are not effected by this.
Second Stomach	"More HP From Medkits" Health drops give +4 HP instead of +2, which also effects Robot's active. Health chests give +8 HP instead of +4. Bloodlust is not effected.
Sharp Teeth	"Damage Taken Is Dealt To All Enemies On Screen" Any health lost will cause damage to be dealt back to all enemies on screen for 2.5x the amount. Unlike any other thing in the game this damage is not rounded; enemies will take the exact amount which can leave their HP in the decimal points. If more damage is taken then the player has health, it will not cause additional damage to be dished out. This is only based on health lost. Taking 0 damage (such as Boiling Veins immunity or headless Chicken) will not proc Sharp Teeth. Sharp Teeth's damage will 'travel' to on-screen enemies, damaging those closer sooner, and will only initiate damage when reaching them if the enemy does not yet have iframes. This means that Sharp Teeth can multi-damage if the player is damaged in quick succession, but damage spread slightly apart may not all go through.
Shotgun Shoulders	"Shells Bounce Further" Most shell weapons will maintain most of their momentum when bouncing off walls. Shells normally deal extra 'point blank damage' for the first two frames after being fired; with this mutation it will also apply for the first two frames a shell bounces off of any wall. Flame weapons do not bounce off of walls normally; this lets them bounce once for a short distance. Large Flak Balls and Flak Balls will never bounce off walls, however their smaller pellets can. Pop Gun, Pop Rifle & Incinerator are all effected by Shotgun Shoulders instead of Recycle Gland as they use shell projectiles.
Stress	"Higher Rate Of Fire As HP Gets Lower" Characters have a 100% firerate by default and will gain additional % the lower HP is, with a simple Current HP / Max HP formula. Missing 50% HP (half health) will give a 150% firerate, while missing 100% HP (headless Chicken) will cap out at 200% firerate. This can stack with YV's passive and his Ultra A mutation.
Strong Spirit	"Prevents Death Once Recharges At Full HP In The Next Area" Any lethal hit that player would take instead gets blocked by Strong Spirit, leaving the player at 1 HP. This will give the player 5 frames of invulnerability from all damage sources, including things that can damage through player iframes. However this is a very narrow window. Strong Spirit can be recharged by reaching full HP again on any following level. If the player only has 1 max HP (Melting/Chicken), then Strong Spirit will be permanently consumed if hit. It will only recharge if the player is able to get back to 2 max HP.
Thronebutt	"Upgrades Your Special Ability" Thronebutt will enhance each characters specific active ability. In-depth explanations can be found on each character page. A shortened version of these are: Fish: "Water Boost" Gives infinite roll with more control. Crystal: "Teleportation; Shorter Shielding" Eyes: "Stronger Telekinesis" Melting: "Bigger Corpse Explosions" Plant: "Snare Finishes Enemies Under 33% HP" YV: "BRRRAP" Pop Pop effect is doubled. Steroids: "Firing Gives Ammo For Your Other Weapon; More Effective When Firing Both" Robot: "Better Weapon Nutrition" Eating weapons gives an additional ammo/health drop. Chicken: "Throws Pierce Through Enemies" Rebel: "Higher Ally Rate Of Fire" Horror: "Beam Charges Up Faster; Prolonged Beam Use Heals You" Rogue: "Stronger Portal Strike" Skeleton: "Better Odds" Blood Gamble is less likely to injure Skeleton. Frog: "Toxic Gas Spreads Faster" Big Dog: "Faster Missile And Bullets"
Trigger Fingers	"Kills Lower Your Reload Time" Any time an enemy is killed 40% of the remaining reload time is removed from both held weapons.
Reroll Mutations
Patience	"Mutate Later" Skips the current set, giving a new one upon exiting the next level. Patience will not re-appear if taken.
Last Wish	"Get Full HP And Some Ammo" Last Wish will cure the player back to their max HP. This includes if Chicken has any missing max health. Gives 20 shells, energy, bolts and explosive ammo as well as 200 bullet ammo. If any cursed weapons are being held when this is taken, their cursed effect will be removed. Last Wish also serves as a reroll mutation - feeding the special Ice Flower prop on 5-1 (also spawns in loop) will give access to the secret Jungle area and consume Last Wish. As Last Wish is consumed it is removed from the player's mutation set, which will re-add it to the mutation pool. This means that Last Wish can be taken multiple times in a run.
Secret Mutations
Heavy Heart	"More Weapon Drops" Heavy Heart is a secret mutation that will only appear if 3 of the 6 weapon-specific mutations are taken in a run. Once this condition is met it is guaranteed to be the first mutation slot of the next set seen, will not replace ultras. Weapon mutations include Boiling Veins, Bolt Marrow, Laser Brain, Long Arms, Recycle Gland and Shotgun Shoulders. Any enemy that has a chance of dropping weapons has their chance multiplied by 210%, more than doubling it. Enemies that do not drop weapons will continue not to do so - only Crown of Guns gives a flat increase. Heavy Heart and Crown of Guns can be stacked together.
Ultra Mutations Individual character pages will go into full detail. This is a summary.
Confiscate	"Enemies Sometimes Drop Chests" Fish's Ultra A mutation that has a 20% chance to convert any enemy drop into a chest instead. Ammo drops become ammo chests, weapon drops become weapon chests and health drops become health chests.
Gun Warrant	"Infinite Ammo The First 7 Seconds After Exiting A Portal" Fish's Ultra B mutation that makes ammo not be consumed for the first 7 seconds any time a new stage is entered. Weapon cooldowns still apply normally.
Fortress	"+6 Max HP" Crystal's Ultra A mutation that gives her an additional 6 max HP. Can be stacked with Rhino Skin making the max total 20 HP.
Juggernaut	"Move While Shielded" Crystal's Ultra B mutation that allows her to freely move during her shield time at a slow speed.
Projectile Style	"Telekinesis Holds Your Projectiles" Eyes' Ultra A mutation that brings any active projectiles he shot back to him by using telekensis, and can be held in place around him or fired out another time.
Monster Style	"Push Nearby Enemies Away When Not Using Telekinesis" Eyes' Ultra B mutation that pushes enemies away from him for a radius that covers most of the screen while not using his active ability.
Brain Capacity	"Blow Up Low HP Enemies" Melting's Ultra A mutation that lets him use his active on alive enemies if they're under 5 HP.
Detachment	"3 More Mutations Lose Half Of Your HP" Melting's Ultra B mutation that gives him an additional 3 mutation pools to choose from at the cost of half of his current max HP. Adding extra HP afterwards(Rhino Skin) will not be halved. On Non-Beta, Detachment will repeat the mutation sets seen on levels 8 & 9 and then give a new set. On the Betas, it will give three new sets.
Trapper	"Big Snare" Plant's Ultra A mutation that adds 5 additional snares that surrounds the main one for a total of 6.
Killer	"Enemies Killed On Your Snare Spawn Saplings" Plant's Ultra B mutation that will spawn sapling allies from enemies killed on snares. They will burst into blood explosions upon contact with an enemy or running out of health, which does additional damage and can erase enemy projectiles.
Ima Gun God	"Higher Rate Of Fire" YV's Ultra A mutation that gives him an additional +40% firerate. With his passive this is an overall 60% boost Grants access to YV's Crib.
Back 2 Bizniz	"Free Pop Pop Upgrade" YV's Ultra B mutation that gives an extra pop to his active without costing extra ammo or reload time. Grants access to YV's Crib.
Ambidextrous	"Double Weapons From Chests" Steroids' Ultra A mutation makes weapon chests always drop the same weapon twice, which also means twice the ammo for that weapon type.
Get Loaded	"Ammo Chests Contain All Ammo Types" Steroids' Ultra B mutation makes ammo & present chests now give ammo for all 5 ammo types when opened.
Refined Taste	"High Tier Weapons Only Auto Eat Weapons Left Behind" Robot's Ultra A mutation removes weapons that appear up to 2-1 in the normal drop pool. This means that 28 weapons are removed from the pool bringing possible weapon drops from 108 down to 80. Entering the portal will automatically eat any weapon left behind.
Regurgitate	"Eating Weapons Can Drop Chests Auto Eat Weapons Left Behind" Robot's Ultra B mutation makes any eaten weapon have a ~43% chance of dropping a chest. Entering the portal will automatically eat any weapon left behind.
Harder To Kill	"Kills Extend Bleed Time" Chicken's Ultra A mutation will add 1 second to the headless timer while headless, but will never go above 5 seconds.
Determination	"Thrown Weapons Can Teleport Back To Your Secondary Slot" Chicken's Ultra B mutation that will automatically return a thrown weapon to her secondary slot once it comes to a stop.
Personal Guard	"Start A Level With 2 Allies All Allies Have More HP" Rebel's Ultra A mutation that automatically gives her two allies for free at the start of a new stage, and all allies max health will be at 30 HP instead of 12 HP.
Riot	"Double Ally Spawns" Rebel's Ultra B mutation that lets her summon 2 allies at a time instead of 1, always at the cost of 2 HP.
Stalker	"Enemies Explode In Radiation On Death" Horror's Ultra A mutation that makes destroyed enemies/props that drop radiation upon death will also burst into radiation pellets that cause 1 damage to enemies each.
Anomaly	"Portals Appear Earlier" Horror's Ultra B mutation that will automatically kill every enemy in the level if their combined health totals less than 140 HP.
Meltdown	"Double Rad Capacity" Horror's Ultra C mutation that increases the ultra rad meter from 600 rads to 1,200 rads, allowing for more rad beam or ultra weapon usage.
Super Portal Strike	"Double Portal Strike Pickups And Capacity" Rogue's Ultra A mutation that lets her have up to 6 portal strikes at a time. Canisters will give 2 portal strikes instead; 1 is still consumed per. shot.
Super Blast Armor	"Super Blast Armor" Rogue's Ultra B mutation that when damaged triggers 6 blast explosions around her instead of the usual 3 giving more coverage/range.
Secret Ultra Mutations
Redemption	"Back In The Flesh" Skeleton's Ultra A mutation that will transform him back into Melting. He will automatically be put at level ultra and can choose 8 mutations and ultra. (link logic later)
Damnation	"Fast Reload After Blood Gamble" Skeleton's Ultra B mutation that will remove 80% of a weapons reload speed when it is blood gambled.
Distance	""Rads Can Spawn Toxic Gas" Frog's Ultra A mutation that gives each dropped rad a chance to spawn a toxic gas cloud.
Intimacy	""Continuously Spawn Toxic Gas" Frog's Ultra B mutation that will continually have Frog emit gas while walking or using his active.
Ultra Spin	""Improved Spin Attack" Big Dog's Ultra A mutation that doubles the amount of bullets he shoots at a time for the same ammo cost.
Ultra Missiles	""Missiles Fire Bullets" Big Dog's Ultra B mutation that lets his missile attack shoot bullets in front of them, similar to the boss attack on loop.
Co-Op Ultra Mutations
Blood Bond	"HP Pickups Are Shared" The Ultra A co-op ultra, any health pickup/chest now will apply to both characters.
Gun Bond	"Ammo Pickups Are Shared" The Ultra B co-op ultra, any ammo pickup/chest now will apply to both characters. Whoever picks up ammo will have the drop chances apply to them, and then that ammo type will also be shared with the player. However opening an ammo chest will give ammo both specific to each players' primary weapon independent of each other.